Endeavour Rendezvous Pitch Maneuver
Day 3, STS 130 – Just prior to docking at 12:06 am on February 10, 2010 the crew of the space shuttle Endeavour executed a tightly choreographed back flip in space.
The maneuver, called RPM, exposes the heat shield of the shuttle to the International Space Station crew who photograph it looking for any launch damage. The RPM is preliminary to docking the shuttle with the ISS.
The photographs are studied to determine if the shuttle is safe for re-entry into earth’s atmosphere. If not, the crew of the Shuttle would wait for a rescue shuttle to arrive from earth.
The destruction of the Shuttle Columbia was a result of damage to the heat shield which was ignored. The Columbia overheated on one wing and disintegrated on re-entry.
While it looks like acrobatics in space, the RPM is a very carefully planned and executed move. The distance between the shuttle and ISS is minimized to get the most accurate photographs which could mean the difference between life and death for the crew.
The RPM uses the R-bar and V-bar vector to line up the Endeavour. R-bar is an imaginary line between the ISS and the centre of the earth. V-bar is velocity vector of the ISS.
Endeavour approaches the ISS along the R-bar at about 600 feet (180 meters) which is very close. The 360 degree roll exposes the heat shield allowing the ISS crew to photograph and inspect it.
At this point the Shuttle commander is flying without visuals, since the shuttle is upside down to the space station.
After the inspection is completed, the shuttle moves to a 90 degree angle and moves along the V-bar to carefully approach the shuttle. The V-bar approach results in the actual docking of the shuttle with the space station.
The shuttle crew have practiced the approach in a simulator on the ground. The shuttle has to essentially align itself with the space station, decelerate to .1 feet per second from orbit speed, and move in very carefully to dock with the space station.
Like most of the shuttle missions, RPM is a carefully planned maneuver that still relies on human skill to execute safely.